Hot box detector



y 1965 R. B. BARNES ETAL 3,183,349

HOT BOX DETECTOR 3 Sheets-Sheet 1 Filed 001;. 30, 1959 K065?! eon 1W6MAIL-s FRANK .scHmRz INVENTORS PREAMP r0 RECORDE? SUPPLY 1/7 May 11,1965 R. B. BARNES ETAL HOT BOX DETECTOR 3 Sheets-Sheet 2 Filed Oct. 30.1959 PEA-AMP DIFFEREN T/AL PREAMP ROBERT Bum/MM:

F/FA/v/r .scmmkz IN V EN TORS i 11, 1955 R. a. BARNES ETAL 3,183,349

HOT BOX DETECTOR Filed Oct. 30, 1959 3 Sheets-Sheet 3 JNVENTORS.8084276014046 8451/65 BY FRANK SCI-{MR2 WWA ATTOENEY United StatesPatent 3,183,349 HOT BOX DETECTOR Robert Bowling Barnes and FrankSchwarz, Stamford, Comm, assignors to Barnes Engineering Company,Stamford, Conn., a corporation of Delaware Fiied Oct. 30, 1959, Ser. No.849,782 8 Claims. (Cl. 246169) This invention relates to a hot boxdetector system.

The problem of detecting hot boxes on railroad cars and particularlyfreight cars is a very serious one. -Not only is there danger involvedif a neglected hot box seizes, which sometimes has been known to causederailment, but even where there are no such dire results the train maybe stopped between stations or yards and the cutting out of the carconsumes much time and results in a very substantial additionaloperating expense. Any means of detecting hot boxes should, therefore,be sufficiently sensitive and reliable so that it gives warning for sometime before the box seizes, permitting cutting out the car in questionat the next yard or station and avoiding the tying up of tracks andother expensive delays which occur when a hot box actually seizes.

At first blush the solution of the problem is fairly obvious. All thatmight be expected to be required would be an infrared radiometerdirected toward the correct boxes. In practice there are some seriousoperational problems which must be solved for an ideally reliabledevice. An approach to the solution is described and claimed in U.S.Patent 2,880,309 to Gallagher and Pelino. Essentially the patentdescribes double infrared radiometers alongside the rails, eitheroutside the tracks or inside, which sight along the track at a suitableangle so that they strike the sides of successive journal boxes as atrain moves along. The output of the radiometers is sent to a centrallocation or to the next station or yard and can be recorded. When a hotbox passes, the recorder will show a response which can be distinguishedfrom other normal journal boxes and from external conditions such ascircuit noise and the like. The modification shown in FIGS. 1, 2 and 11of the patent in which the radiometers are outside the tracks, whiletheoretically operative are practically not usable except in fairweather. Infrared radiation is absorbed by solid water and a rainstormmay be so heavy as to render the device of such low and erraticsensitivity as to be impractical. Even in less extreme storms the Waterfrom the whole car top may cascade off one side a sheet of water.

The modification shown in FIGS. 8, 9 and 10 of the Gallagher patent, inwhich the radiometers are located just inside the rails, is morepractical as the passing cars serve as umbrellas and prevent heavysheets of rain from falling between the radiometer and the wheel journalor other portion, the temperature of which is to be measured. Thispermits operation on many rainy days but still does not take care of thesituation presented when heavy rain and high wind occur at the same timeon open stretches of track. The rain then blows in sideways and againthe devices becomes unsatisfactory. Days of this nature are somewhatless frequent than days with heavy rain, with or without wind, but theyare sufficiently frequent so that the instrument is not reliable theyear around.

An essential and fundamental disadvantage of the Gallagher device isthat it requires four radiometers in order to be useful for themeasurement of the temperature of journal boxes and adjacent metalparts. This is an essential limitation because, as the patenteescorrectly realized, the front edge of an approaching journal box may notbe at the same temperature as the rear edge because the front edge issubjected to a blast of cooling air whereas the air adjacent to the rearedge is relatively stagnant. As a result it is necessary to haveseparate radiome- 3,183,349 Patented May 11, 1965 ice ters facing inopposite directions for each track. These are associated with switchesor other devices actuated by the wheels so that the proper radiometer iscut into circuit depending on the direction in which the car istraveling on the track. Even when the correct radiometer is cut in sothat it views receding cars, there are differences between the journalsof a single bogie because of intervening members which obscure onejournal more than the other when viewed along a path nearly parallel tothe rails. Other disadvantages of the device of the Gallagher patentwill be referred to below in connection with the description of thepresent invention which eliminates all of the disadvantages.

Essentially the present invention comprises two radiometers, or in amore specific aspect two optical systems, with a single detector mountedmore or less centrally between the tracks and receiving radiation froman upwardly inclined direction substantially at right angles to therails instead of predominantly from a direction along the rails as isspecified as an essential requirement of the device of the Gallagherpatent. The radiometers of the present invention receive radiation fromportions of the inner part of the wheel as is the case with the deviceof the Gallagher et a1. patent shown in FIGS. 8 and 9. However, theyreceive this radiation in a direction substantially at right angles tothe rails instead of essentially along them as in FIG. 8 of Gallagher orparallel to the plane thereof and straight up as in FIG. 9 whichGallagher et al. themselves agree is not satisfactory as it exposes theoptics to dirt and weather.

There is a choice of what portion of the Wheel is viewed by theradio-meters. It can be an part of the inner surface but is preferablythe junction of the axle and the wheel. It has been found that herethere is the greatest rise in temperature with development of hot boxesand the effect of heating of the periphery of the wheels by brake shoesis minimized. However, there is sufiicient rise in temperature adjacentto the junction of axle and inner wheel surface so that the invention isnot absolutely limited to viewing precisely the junction of wheel andaxle. In general, however, the greater efliciency of this viewinglocation renders it the preferred embodiment of the invention. It willbe seen that two radiometers, both fully protected from the weather bythe viewing angle, which is not too far removed from the horizontalplane, perform the same function as four radiometers in themodifications of the Gallagher patent which are practically useful andin which protected radiometers are used, viewing in general, along thetracks. In other words, the same effect of measuring the temperaturedeveloped by the journals of wheels in cars going in either directionalong the rails is effected with half the number of parts. In a morespecific modification of the device still further saving of parts ismade possible.

The invention will be described in greater detail in conjunction withthe drawings in which:

FIG. 1 is a perspective of a freight car bogie on the track;

FIG. 2 is a schematic detail in section of optics using separatedetectors;

FIG. 3 is a schematic in section of reflective optics using half thenumber of detectors;

FIG. 4 is a schematic in section of different reflecting optics usinghalf the number of detectors;

FIG. 5 is a perspective similar to FIG. 1 showing an additionalcomparison radiometer, and

FIG. 6 is a schematic diagram of a typical transistor amplifying andgating circuit.

In FIG. 1 the rails are shown at 1 with conventional cross ties at 2 anda separate mounting tie 3 between the regular ties and having mountedthereon a twin radiometer 4 shown as receiving rays from the junctions 5of axle and wheel. The wheels and axles are shown in the conventionalbogie which comprises frame 8, springs 9, wheels ill, axles l1 andjournal boxes 12. It will be noted that a twin radiometer, instead oftwo twin radi ometers, perform the same function as is performed by theonly, at least partially practical, modification of the Gallagher patentin FIG. 8. There is a further preferred element of design, namely, thatthe radiometer is mounted on a separate tie which is not connected tothe rails instead of on the regular ties as in the Gallagher patent.This avoids the major portion of the low frequency vibration caused bythe passage of the railroad cars. In the Gallagher device the mountingis on the tie which receives this vibration without any diminution. Thatthis problem is a serious one was realized by Gallagher who suggestsusing a shock mounting'in his FIG. 4.

Shock mounting is helpful even in the devices of the present inventionif vacuum tube amplifiers are used in the radiometer itself. It is lessnecessary when separate mounting ties or bases are used as in thepresent invention and when transistorized amplifiers are used which arepreferred in the devices of the invention, no shock mounting need beprovided where there is a separate mounting base. It should be notedthat when the mounting is on the tie itself the vibration may be sointense that even parts of the radiometer other than tube amplifiers maybe adversely affected. It should be noted that the central mounting ofthe radiometers of the present invention minimize the effect ofvibration as their location is about as far. from both rails aspossible.

FIG. 1 illustrates one further desirable feature though it is notabsolutely essential. This feature employs drainage pipes to keep thearea between the ties where the double radiometer is mounted fromfilling with water in the .vent of severe rain or melting snow. Thereisfairly good drainage in well ballasted track using rock ballast and soin most locations it is possible to operate without special drainagemeans. However, they are desirable and so in preferred aspects of thepresent invention are included.

In order to determine where a hot box is located as a train moves past,some axle counting device is desirable. A typical such wheel actuateddevice is shown in the Gallagher patent and it is an advantage of thepresent invention that any suitable counting device may be used. At thesame time the wheel actuated switch, which is shown at '7 as of themagnetic type, can perform an additional function. That is to say it canbe used as a gate or more precisely to trigger a gating transistor forthe electrical systems receiving signals from the radiomeeters thuscausing the circuits to be open only when the radiometers view apredetermined portion of the wheel, for example, the junction of axleand wheel. The gating in the electronic circuits may be of standarddesign and it is an advantage of the present invention that no specialor complicated circuitry is needed. The electronic circuits are,therefore, not shown, only the wheel actuated device 7 being illustratedin diagrammatic form. The only difference of significance lies in thedesirability of using transistorized amplifiers to eliminate .microphonic problems and for minimum power consumption and maximum life. Theradiometers, or. more correctly the twin radiometer of the presentinvention, views the passing wheel axle junction for only a few inchesand the time during which the detector receives radiation is, therefore,dependent on the speed of the train. This constitutes no practicalproblem although it is a necessary limitation of the present invention.In general, with maximum freight train speeds of about 70 miles an hour,the viewing time is of the order of 5 milliseconds. The calculation isas follows: 70 m.p.h.= 103 ft./sec. As the area observed on the wheel isabout 6 this corresponds to 4.9 milliseconds. Infrared detectors of ashorter response time, for example, of the order of l or 2 milliseconds,are standard articles of commerce and, therefore, while the presentinvention requires detectors of fast response this is not a practicallimitation since it merely determines the choice of known conventionaltypes of detectors. These high speed detectors are ordinarily of smalldimensions and this in turn may affect the choice of a particular typeof optics, namely, those which are substantially achromatic over theinfrared energy band to be received. Theoreticallylenses or lense filtersystems which are achromatic over a wide band of infrared radiationcould be used. However, ordinary lens materials show considerablechromatic aberration and therefore, in general, the optics shown in theGallagher patent, which employ ordinary conventional infrared lenses,are not suitable for the present invention because the chromaticaberration results in the focusing of different wavelengths of theinfrared radiation in different planes of the small fast detectors.However, the most serious loss with most infrared, lenses lies in thefact that most materials cut off a considerable portion of the farinfrared, for example, beyond 15 microns. With the fairly lowtemperatures that are being measured a considerable portion of theenergy is radiated in this region. Therefore, most lenses utilize only aportion of the infrared energy radiated. The present invention,therefore, prefers infrared optics, particularly reflective optics,which utilize the energy more efficiently and, therefore, may beconsidered more efficient.

Another method for handling the problem of detector time constant is touse electronic amplifiers which amplify more strongly the changes indetector output rather than solely the amount of voltage generated. To aconsiderable extent such amplifiers can compensate for somewhat slowerdetectors. These amplifiers normally operate by boosting the highfrequency response.

Three representative types of reflective optics are shown in FIGS. 2 to4, the same elements bearing the same reference numerals. In all threefigures there are present two converging mirrors 13. Three types ofmirrors are shown in the different figures, ordinary condensing mirrorsin FIG. 2, Cassegrain mirrors with reflecting mirrors 14 in FIG. 3 andNewtonian condensing mirrors with reflecting mirrors in FIG. 4. In FIG.2 there are two separate detectors of conventional design, that is tosay, having at detecting element 15 receiving the radiation and asimilar element 16 connected in opposition to balance out changes inambient conditions. The detectors, which are illustrated as preferablyof the thermistor type, but may be other types of infrared sensitivedetectors, are energized by a bias supply 17 and the differential outputis fed to a conventional preamplifier 18, the output of which can be ledto the telemetering systems, recorders, alarms, etc.

In FIG. 3 there is illustrated a twin radiometer with only half as manydetector elements. Here each detector receives radiation from the wheelsbut the two detectors are connected in opposition so that only adifference voltage is applied to the preamplifier. This requiresreasonably matched detectors but has the advantage that the number ofelements is halved; in other words, in this modification two detectorflakes take the place of the eight flakes which are needed in thepractical modifications of the Gallagher patent.

FIG. 4 illustrates a different use of two detectors by feeding theiroutput into a differential preamplifier 19. While this is a differenttype of amplifier than that shown in FIG. 3 it is also conventional andso is shown only diagrammatically.

FIG. 6 illustrates a typical transistor amplifying and gating circuit.The values of the components are given but only some of the componentsare designated by reference numbers. The diagram shows the twothermistors l5 and 16 and their bias source 17 in schematic form. Thedifferential signal from the thermistors enters the amplifying circuitthrough the large capacitor 24 which,

with the associated circuit constants, results in a time constant ofsuitable length so that the response of the instrument does not changesignificantly with the speed of the railroad train up to a maximum ofabout 70 miles per hour.

Essentially the first part of the amplifier is a standard A.C. amplifierwith a fairly long time constant so that there is no continuing signalbeyond the approximately 5 millisecond interval. The output which is inthe form of a broad pulse determined by the time constant of thepreamplifier, passes on through the capacitor 25 which blocks directcurrent signals. Capacitor 25 connects to the base of the gatingtransistor 27, which is normally biased to cutofi and so does notamplify any signal.

When a train wheel passes the magnetic switch 7 (representedschematically on FIG. 6 as an inductance), a pulse results which isclamped to a certain voltage by the diode 21 and is amplified and passedby the diode 22 to the transistors forming a conventional flip flopcircuit. The output of this circuit, clamped by the diode 23, is appliedto the base of the transistor 26. This transistor is normally biased tocutoif and hence does not affect the voltage on the base of the gatingtransistor 27. When, however, the amplified pulse from the magneticswitch actuates the flip fiop circuit, a positive voltage is applied tothe base of transistor 26, causing the latter to conduct. As a resultthe transistor 2s presents very low resistance and for practicalpurposes brings the base of the gating transistor to ground potential.This causes the transistor to be biased in operating condition, i.e.,the gate is opened and any amplified signals from the thermistors and 16are amplified by the gating transistor 27 and its succeeding transistor,and a signal output in the form of a pulse results.

When the train is moving at 70 miles an hour or more the next pulse fromthe magnetic switch 7, caused by the partial collapse of its magneticfield, is amplified and resets the flip flop circuit to its originalstate. The transistor 26 ceases to conduct, the gating transistor 27 isbiased to cutoff, and the gate is closed. If, however, the train ismoving very slowly, signals from the thermistors 15 and 16 will cease tobe amplified after a short period of time determined by the timeconstant of the input circuit to the preamplifier of which capacitor 24is one element. The duration of the pulse is, therefore, determinedeither by the opening and closing of the gate due to signals from themagnetic switch 7, or by the effect of the time constant of thepreamplifier, whichever is shorter. In the unlikely event of speedsabove 70 miles per hour the magnetic switch will close the gate after aperiod somewhat shorter than 5 milliseconds. This will result in anarrower pulse with a little less energy, but the occurrence is rare andthe shortening of the pulse duration is too small to affect seriouslythe signal from the gated amplifier circuit.

Theoretically it might be argued that the record of two hot boxes on thesame axle would cancel out and so would not record the presence of a hotbox. It should be noted that they would have to be exactly the sametemperat'ure at both ends of the axle which makes the likelihood of twoincipient hot boxes on the same axle having the same temperature toosmall to be considered, as the probability of such an occurrence isextremely remote. It is, however, possible, particularly with adifferential preamplifier, as shown in FIG. 4, to prevent even such anextremely improbable occurrence from causing the machine to fail to givean indication of an incipient hot box. This can be simply taken care ofby taking ofi a portion of each detector signal before they are combinedto produce a differential output and using these signals to actuate analarm system. If either or both show excessive outputs, this can be fedinto the recorder, if desired through suitable threshold circuits, sothat if the signal is large enough from either detector a record willappear. It is an advantage of the present invention that in manyinstallations it is not necessary to provide for the unlikely occurrenceof two incipient hot boxes of the same temperature on the same axle, ifit is desired this additional protection may be obtained.

FIG. 5 illustrates in perspective a somewhat more elaborate device. Thecorresponding parts bear the same reference numerals as in FIG. 1. Ithas been found that the part of the axle and wheel assembly which ismost nearly constant in its temperature, once it has adjusted itself toambient conditions, is the middle of the axle. This can, therefore, beused as a reference point and in FIG. 5 a third radiometer 20 ispositioned with its beam pointing substantially at right angles to thetrack and upward so that the center of the axle is imaged at the timewhen the other radiometers are receiving their infrared radiation fromthe wheels or as in the preferred modification from the point where theaxle joins the wheel. A comparison is thus possible which under certaincircumstances gives a more reliable indication than do the tworadiometers alone. For example, if a differential signal or adifierential signal amplifier is used, as in FIGS. 3 and 4, the outputsignal is determined by the relative temperatures of the two wheels.Under certain extreme climatic conditions a difference may be caused bysomething other than a hot box. For example, in the case of a sleetstorm blowing across the track, one side of a freight car, including itswheels and bogie frame work, may be coated with ice. This may result ina lower temperature for the corresponding wheel, particularly if brakeshave been applied which would warm up the wheel not coated with ice,while the ice coating to a large extent absorbed the braking heat aslatent heat of fusion. A similar situation might result if a freight carhad been standing with an intense summer sun beating on one side. Againthe wheels on the different side of the car may be at differenttemperatures. In each case the center of the axle would be leastaffected and can be used as a reference point. For example, theradiometer 20 may feed a signal which is compared with the signals fromthe other two radiometers and an alarm only registered if there is atemperature difference of significance between the center of the axleand the wheel which is getting heated by an inadequately lubricatedhearing.

The decision as to whether a device similar to FIG. 5 is to be used orthe simpler device of FIG. 1 would be largely dictated by economic andgeographical considerations. The additional radiometer, of course, addsto the cost of the device and so the more elaborate device wouldnormally be used only where climatic conditions are such that theadditional reliability is worthwhile. Since the most serious climaticcondition is a heavy sleet storm the simpler device will frequently bepreferable in the south where such conditions do not occur. However, itis an advantage of the present invention that it is quite flexible andthat devices of differing degrees of complexity and function areavailable to suit every condition.

It has been proposed to use a plurality of hot box detectors atreasonably close intervals, for example, two or three miles so thatthree readings could be consulted for, of course, the most reliableindication is a rapid rise in temperature. The idea of multipleinstallations to achieve the above desired result is not our invention.Reference thereto, however, is made here because the devices of thepresent invention are very suitable in such a system. Also, when thereare several detectors which will be considered in series, the risk of afalse indication by reason of laterally asymmetric temperatureconditions is minimized for a differential temperature reading betweenwheels on the same axle would not be as significant if there were nochange through successive hot box detectors. Therefore, when themultiple hot box detector is used it will often be consideredeconomically possible or desirable to use the simpler device of FIG. 1whereas under the same geographic conditions if only a single detectorwas being provided the more accurate reading of the device of FIG. mightbe found preferable.

FIGS. 2 to 4 show different achromatic optics associated with differentdetector designs. It will be understood that any one of the achromaticoptics can. be used with any one type of detector.

While the largely horizontal direction of the infrared path furnishesconsiderable protection of the mirrors from the elements it is desirableto use a suitable infrared window such as a thin sheet of polyethylenein order to keep out dust. Thesheet'can be backed up with aperforatedmetal plate for greaterzstrength.

We claim: v

1; A hot box detector comprising "in combination a lengthofrailroadtrack, an infrared detection device mounted between the railsof said track, said detection device comprising infrared detectors andoptical means with substantially uniform transmission through apredetermined wavelength band imaging each infrared detector along anaxis inclined upwardly with respect to the track elevation andsubstantially at right angles to the track, the

' inclination of the axis being such as to image a portion of thecentralpart ofrailfroafd';.- .car yzheelspassing overthe said infrareddetection device whereby infrared energy radiated from said centralportion of the railroad car wheels along said axis is shielded from rainfrom both *top and sides as an axle passes over the detecting device.

2. A hot box detector according to claim 1 in which the infrareddetectors comprise a single detector each connected in oppositionwhereby the detectors produce a differential output signal. 7

3. A'hot box detector according to claim 1 including wheel responsivemeans for actuating the infrared detecting device for a predeterminedtime interval as each pair of railroad carwheels pass over the detector.

4. A hot box detector according to claim 3 in which the infrareddetectors have a response time not exceeding 5 milliseconds.

5. A hot box detector according to claim 3 in which 5:3 the infrareddetectors each consist of a single detector bridge circuit, the outputsthereof being connected in opposition whereby a differential outputsignal is produced.

6. A hot box detector according to claim 1 in which the imaging meansimage the infrared detectors on the junction of the railroad caraxle'with the wheel.

7. A hot box detector according to claim 3 in which the imaging meansimage the infrared detectors on the junction of the railroad car axlewith the wheel.

8. A hot box detector according to claim -1 in which the output of theinfrared detectors are energized and their output amplified by fullytransistorized equipment.

References Cited by the Examiner UNITED STATES PATENTS 1,901,192 3/33Reinhardt et al. 73-355 2,376,311 5/45 Hood. 2,565,249 8/51 Machler73-355 2,710,559 6/55 Heitmuller et al. 2,818,508 12/57 Johanson et al246-169 X 2,829,267 4/58 Howell 246-169 2,856,539 10/58 Orthuber et al.246-169 2,880,309 3/59 Gallagher et al. 246-169 ;2,920,485 l;/ Derganc;73-355 2,963,575 12/60 Pelino et al. 246-169 3,065,347 11/62 Bossart246-169 X FOREIGN PATENTS 1,199,244 6/59 France.

940,785 3/56 Germany. 1,031,338 6/58 Germany.

705,327 3/54 Great Britain.- 328,951 3/58 Switzerland.

7 oTHER REFERENCES- S.H.A. (1), German application 1,002,381, printedFeb. 14, 1957 (KL 20h).

LEO QUACKENBUSH, Primary Examiner. JAMES S. SHANK, LEO J. LEONNING,Examiners.

1. A HOT BOX DETECTOR COMPRISING IN COMBINATION A LENGTH OF RAILROADTRACK, AN INFRARED DETECTION DEVICE MOUNTED BETWEEN THE RAILS OF SAIDTRACK, SAID DETECTION DEVICE COMPRISING INFRARED DETECTORS AND OPTICALMEANS WITH SUBSTANTIALLY UNIFORM TRANSMISSION THROUGH A PREDETERMINEDWAVELENGTH BAND IMAGING EACH INFRARED DETECTOR ALONG AN AXIS INCLINEDUPWARDLY WITH RESPECT TO THE TRACK ELEVATION AND SUBSTANTIALLY AT RIGHTANGLES TO THE TRACK, THE INCLINATION OF THE AXIS BEING SUCH AS TO IMAGEA PORTION OF THE CENTRAL PART OF RAILROAD CAR WHEELS PASSING OVER THESAID INFRARED DETECTION DEVICE WHEREBY INFRARED ENERGY RADIATED FROMSAID CENTRAL PORTION OF THE RAILROAD CAR WHEELS ALONG SAID AXIS ISSHIELDED FROM SAID RAIN FROM BOTH TOP AND SIDES AS AN AXLE PASSES OVERTHE DETECTING DEVICE.